DESCRIPTION (Investigator's Abstract): Using currently available technology, approximately 50 percent of patients with malignancies may be cured. Of the remaining 50 percent, a majority die from the effects of metastatic burden. Metastasis is a complex multistep process in which tumor cells escape the primary tumor site and establish secondary tumors in distant organs. The formation of metastases is dependent upon the successful completion of each step. The failure of any one step could abort the entire process. An important step in the metastatic process is the crossing of the basement membrane(BM). Each trip across the basement membrane requires the hydrolysis of collagen IV. Metastatic tumor cells use the metalloprotease collagenase IV to selectively hydrolyze collagen IV. Inhibition of collagenase IV is seen as a possible method for controlling metastasis and increasing patient survivability. Despite its suggested role in the metastatic process, little attention has been given to the production of collagenase IV inhibitors. The goal of the proposed research is to produce potent and selective inhibitors of collagenase IV to be used as antimetastatic agents. Synthetic hexapeptide substrates, that are selectively hydrolyzed by collagenase IV, will be used as models for the design of inhibitors. The Gly-X dipeptide, which contains the scissilepeptide bond, will be replaced with one of two non-hydrolyzable dipeptide isosteres, which are designed to mimic the transition state. In the firstseries of inhibitors, the Gly-X dipeptide will be replaced with an alpha, alpha-difluoroketomethylene isostere. Isosteres of this type have been used previously with great success in producing inhibitors of proteolytic enzymes. The second series of inhibitors will contain various alpha, alpha-difluoroketoethylene isosteres. These isosteres, which more accurately mimic dipeptides, have not yet been used to produce enzyme inhibitors. Amino acids will be added to either or both sides of the dipeptide isosteres, producing inhibitors of various lengths. The inhibitors will be assayed for their ability to inhibit purified collagenase IV and for their ability to inhibit the metastatic process in mice. The inhibitors will also be tested for the ability to inhibit other physiologically important proteases such as interstitial collagenase and stromelysin. Activity against the three enzymes will be correlated with inhibitor length, amino acid content and dipeptide contained within the inhibitor structure to determine what effect each of thesefactors has in determining inhibitor potency and selectivity.